I have a check engine light on my dash. When I got the code for the engine light, it came up with P0420 Catalyst Efficency Below Threshold (Bank1) error code.

Now, I know there could be multiple issues why this code appears. I know that its either my Oxygen Sensors or even worst, my Cadilac Converter. I was just wondering, how many Oxygen Sensors are there in my vehicle? and how can I determine which Oxygen Sensors to replace?

I'm pretty sure there are 4 Oxygen Sensors in my car, 2 in the front of the cadilac converter and 2 in the back. Can this error code determine which O2 censors it is?? I just don't want to replace the wrong ones and spend more money than I have to.

I got this car with 80,000 miles on it and had it for a year now and it has 91,000 miles on it now. When I got iti inpected my torque converter died the week before I went to get it inspected, and now I have to replace either the oxygen sensor or the cadilac converter to get it inspected. Becuase where I'm from, you cant get a car inspected with the Check light on your dash, they will fail you cuz of that. Also, I have to replace the transmission mount and lower ball joints. This car has been costing lots of money. So i really hope I just have to replace the Oxygen Censors instead of the Cadilac Converter.

If you have a scanner, you can erase the code and take a long highway drive to see if it comes back. Maybe your catalytic converter needs some extra flow and heat to get it cleaned out. I had a CEL when I picked up my car after it had been parked for about 8 months at my inlaws, and it only took about 500 miles of driving to get it to turn off. I was pretty sure this had something to do with the computer re-learning the proper fuel-air ratio to cooperate with the catalytic converter. Other than that, my Subaru Outback sometimes gives a similar type of code if one of two things is wrong: 1. Gas cap is loose/missing/malfunctioning, 2. Catalytic converter is below efficiency.
Hope this helps!

On another note: All cars need a little bit of TLC to keep going. Your car is coming up on almost 14 years old and it needs maintenance. (Get used to it, that is the way life is.) I personally think that if it is taken care of, your car could make it to 300,000 miles and you still will not have spent what it would have cost to buy another car that might also require all sorts of maintenance. (This is assuming that you don't get all of your work done at Stealerships and crooked mechanic shops.)

If you have a scanner, you can erase the code and take a long highway drive to see if it comes back. Maybe your catalytic converter needs some extra flow and heat to get it cleaned out. I had a CEL when I picked up my car after it had been parked for about 8 months at my inlaws, and it only took about 500 miles of driving to get it to turn off. I was pretty sure this had something to do with the computer re-learning the proper fuel-air ratio to cooperate with the catalytic converter. Other than that, my Subaru Outback sometimes gives a similar type of code if one of two things is wrong: 1. Gas cap is loose/missing/malfunctioning, 2. Catalytic converter is below efficiency.
Hope this helps!

On another note: All cars need a little bit of TLC to keep going. Your car is coming up on almost 14 years old and it needs maintenance. (Get used to it, that is the way life is.) I personally think that if it is taken care of, your car could make it to 300,000 miles and you still will not have spent what it would have cost to buy another car that might also require all sorts of maintenance. (This is assuming that you don't get all of your work done at Stealerships and crooked mechanic shops.)[/b]

My father is a retired mechanic and he always lets me know when its time to replace a part on the car. I go to him every month to get a check up on the car. I change the oil every 2,000 miles and had 1 transmisison flush when I first got it at 80,000 miles. So, I take really good care of the car and thats why its soo frustrating to me why this is happening. I replaced exhaust piping also through out the muffler of my vehicle as well. I clean the egine and get new air filters every oil change too. The car is in extremly good condition with only 90,000 miles on it. Its all leather (no holes, still looks brand new) with power everything and a power sunroof as well. I like the car a lot and take good care of it....I just hope I dont have to replace the Cat.

With the P0420 error code, it states "Bank 1". Is there a way to find out which censors I should replace, the front or the back sensors? I know there is 4 sensors all together, just want to know before I rip into this becuase I dont want to waste my time and chekcing the wrong end of the Cat.

Thanks for your help in advance!!!!

PS: This website is awesome! I've learned many things from this site about my car and the people on here are smart and caring people! This site helps a lot when it comes to repairs and tips or hints. on taurus cars.

So I can trick the CAT?? If my Cat is bad...I really dont have the money to replace it. Until I have money, I just need to get it inspected.

Does tricking the sensor actually work?? Is there a more detailed explanation on how to trick the CAT so the "Check Engine" light wont come on and I can pass my Inspection and Emissions test??

What they do is, they just put the car on a machine to see if it will pass emissions, thats it. I already got an inspection sticker, just need emissions. They put the car on the machine and tells them weather the emissions is bad or good.

Can you supply a step by step guide on how to do this or another website with a more detailed description on how to trick the CAT?? Becuase this will be my option until I can replace the CAT. Im going to replace the O2 sensors first and see if it works. If not, then Im going to trick the CAT...thanks in advance for your help.

I love the non-fouler trick! Works great. Definitely do what the first poster said: drive it on the highway for like 60 minutes and then erase the code. It might not come back.[/b]

I drove on the highway for over an hour to see my friend. The light still wont go away but I did not erase the code becuase I dont know how. How do I erase the code??? Do you think I should drive again for like an hour and erase the code after I figure out how to erase the code or should just erase the code as soon as I find out how to and not drive for over an hour again???

I drove on the highway for over an hour to see my friend. The light still wont go away but I did not erase the code becuase I dont know how. How do I erase the code??? Do you think I should drive again for like an hour and erase the code after I figure out how to erase the code or should just erase the code as soon as I find out how to and not drive for over an hour again???[/b]

Go to autozone and ask them to erase your code. Or disconnect the battery for 15 minutes works also. But disconnecting the battery will also erase other settings like radios and stuff.

QUOTE (Skrilla @ Jan 6 2010, 12:20 PM)

Quote:

Would I have to remove the CAT comletely to have this work??[/b]

NO. It's very easy to do. The whole idea is that the rear O2 sensor is what monitors whether the CAT works or not. If the CAT is working, then under "normal" driving conditions (i.e. not accelerating hard or something like that), the rear O2 sensor should NOT switch. This is because the CAT has successfully converted the unwanted species to CO2 and O2 and whatever else so the reading is constant (around 0.75mV or so). If your CAT is dead, then unwanted species like CO, hydrocarbon, NOx will pass thru, which causes the O2 sensor to switch between 1 and 0 volt output. The idea of the non-fouler trick is to shield the O2 sensor enough so that it doesn't get a full reading of the exhaust. In other words, it is damping the response of the sensor.

All you need to do to make it work is buy a non-fouler, screw the O2 sensor into it and then screw the non-fouler into the exhuast port where the O2 sensor was. Sometimes, one non-fouler is not good enough. So some instruction have you first drill out one non-fouler. Then put the O2 sensor in that. Then put this non-fouler in the other non-fouler and then screw the entire unit into the exhaust port. Note that you only do this non-fouler thing for the O2 sensor AFTER the catalyst. There should be 2 O2 sensors AFTER the TWO cats. But you only need to do it for the bank that's throwing the code.

Moral of the story: if you go with double non-fouler on each O2 sensor, then you need 4 non-foulers. You need to remove the two post-CAT O2 sensor and then install the non-foulers. Very easy to do and is very effective. People often do this after they delete the CAT so that there's no CEL. On post-2006 cars though, I think the emission checking system in the car has advanced so that this will throw off other codes.

I had a similar problem. It turned out to be the oil pan gasket. Oil was leaking and blowing back on the O2 sensor causing it to read erroneously. Replacing the oil pan gasket and cleaning the outside of the O2 sensor cured the problem on a 96 Duratec.

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